```pascal
FUNCTION "SpeedAdjust" : Real
{ S7_Optimized_Access := 'FALSE' }
AUTHOR : 'Author'
FAMILY : 'Function'
NAME : 'Name'
VERSION : 1.0
   VAR_INPUT 
      i_PrdTnkLvl : Real;
      i_TrgTnkLvl : Real;
      i_IstLvl : Real;
      i_SpeedPerc : Real;
   END_VAR

   VAR_TEMP 
      m_SpeedPerc : Real;
      a : Real;   // Angolar Coefficient
      b : Real;   // Constant
      mCalc : Real;
   END_VAR


BEGIN
	
	
	  //  The following function calculates the percentage speed correction to get Product Tank target Level
	  //    the equation used is: y = a * PrdTankLvl + b ; that is a = - SpeedPerc / IstLvl; and b = 1 - TrgTnkLvl * a
	  //    the function yelds 1.0 at 50% of level; (1 - SpeedPerc) at 80% level; the maximum is (1 + SpeedPerc) 
	 
	
	#m_SpeedPerc := #i_SpeedPerc / 100 ;
	
	IF #i_IstLvl > 0 THEN
	    #a := -#m_SpeedPerc / #i_IstLvl ;
	    #b := 1 - (#a * #i_TrgTnkLvl) ;
	    #mCalc := #a * #i_PrdTnkLvl + #b  ;
	    #SpeedAdjust := LIMIT(MN:=1 - #m_SpeedPerc,IN:= #mCalc ,MX:= 1 + #m_SpeedPerc) ;
	ELSE
	    (* classic code: #SpeedAdjust := 0.0 ;*)
	    #SpeedAdjust := REAL#0.0 ;  
	END_IF;
	
	
END_FUNCTION


```